﻿using System;

namespace Apewer.WinForm
{

    /// <summary>修饰键。</summary>
    public struct ModifierKey : IEquatable<ModifierKey>
    {

        byte _value;
        bool _alt;
        bool _ctrl;
        bool _shift;
        bool _win;

        /// <summary>包含 ALT 键。</summary>
        public bool WithALT { get => _alt; }

        /// <summary>包含 CTRL 键。</summary>
        public bool WithCTRL { get => _ctrl; }

        /// <summary>包含 SHIFT 键。</summary>
        public bool WithSHIFT { get => _shift; }

        /// <summary>包含 WIN 键。</summary>
        public bool WithWIN { get => _win; }

        /// <summary>修饰键组合的值。</summary>
        public byte Value { get => _value; }

        /// <exception cref="OverflowException"></exception>
        private ModifierKey(byte value)
        {
            _alt = value << 7 >> 7 == 1;
            _ctrl = value << 6 >> 7 == 1;
            _shift = value << 5 >> 7 == 1;
            _win = value << 4 >> 7 == 1;
            _value = Convert.ToByte(value);
            if (_value != value) throw new OverflowException($"参数【{value}】含有无效的键。");
        }

        private ModifierKey(bool alt, bool ctrl, bool shift, bool win)
        {
            _alt = alt;
            _ctrl = ctrl;
            _shift = shift;
            _win = win;

            var value = 0;
            if (alt) value += 0x01;
            if (ctrl) value += 0x02;
            if (shift) value += 0x04;
            if (win) value += 0x05;
            _value = Convert.ToByte(value);
        }

        /// <summary></summary>
        public override int GetHashCode() => _value;

        /// <summary></summary>
        public override bool Equals(object obj)
        {
            if (obj is ModifierKey b) return _value == b._value;
            return false;
        }

        /// <summary></summary>
        public bool Equals(ModifierKey another) => _value == another._value;

        /// <summary></summary>
        public static implicit operator byte(ModifierKey instance) => instance._value;

        /// <summary></summary>
        /// <exception cref="OverflowException"></exception>
        public static implicit operator ModifierKey(byte value) => new ModifierKey(value);

        /// <summary></summary>
        /// <exception cref="ArgumentException" />
        public static ModifierKey operator +(ModifierKey a, ModifierKey b)
        {
            if (a._alt && b._alt) throw new ArgumentException("相加的两个组合键共同包含了 ALT 键。");
            if (a._ctrl && b._ctrl) throw new ArgumentException("相加的两个组合键共同包含了 CTRL 键。");
            if (a._shift && b._shift) throw new ArgumentException("相加的两个组合键共同包含了 SHIFT 键。");
            if (a._win && b._win) throw new ArgumentException("相加的两个组合键共同包含了 WIN 键。");

            var alt = a._alt || b._alt;
            var ctrl = a._ctrl || b._ctrl;
            var shift = a._shift || b._shift;
            var win = a._win || b._win;
            return new ModifierKey(alt, ctrl, shift, win);
        }

        /// <summary></summary>
        public static ModifierKey operator -(ModifierKey a, ModifierKey b)
        {
            var alt = a._alt;
            var ctrl = a._ctrl;
            var shift = a._shift;
            var win = a._win;

            if (b._alt) alt = false;
            if (b._ctrl) ctrl = false;
            if (b._shift) shift = false;
            if (b._win) win = false;

            return new ModifierKey(alt, ctrl, shift, win);
        }

        /// <summary>表示 ALT 修饰键。</summary>
        public static ModifierKey ALT { get; } = new ModifierKey(0x01);

        /// <summary>表示 CTRL 修饰键。</summary>
        public static ModifierKey CTRL { get; } = new ModifierKey(0x02);

        /// <summary>表示 SHIFT 修饰键。</summary>
        public static ModifierKey SHIFT { get; } = new ModifierKey(0x04);

        /// <summary>表示 WIN 修饰键。</summary>
        public static ModifierKey WIN { get; } = new ModifierKey(0x08);

    }

}
